Shark Attack Victim: 'I Was Staring at It Eyeball-to-Eyeball'

Steven Robles got a little more than he bargained for on his usual morning swim this weekend – a 7-foot great white shark.

The Keller Williams Palos Verdes Realty broker, 50, was nearing the end of a one-hour swim from Southern California's Hermosa Beach to Manhattan Beach with a group of 14 friends at 9:30 a.m. on Saturday when the shark "came from the bottom of the ocean floor, surfaced at the top of the water, made a very sharp left turn and lunged" at the side of his rib cage, he tells PEOPLE.

"He just swam right at me and when he lunged into my chest, I could feel his whole body vibrating," says Robles, who is an open-water swimmer and completed a 24-mile swim from Catalina Island to Palos Verdes last year. "It happened so quick. I was very scared. It was burning pain. ... I was staring at this shark eyeball-to-eyeball with its teeth on the side of my rib cage."

And though it was "the most frightening thing" he's ever experienced, Robles followed "pure instinct" that saved his life.

"I had enough sense to use my right hand to grab its nose and pry the fish's teeth off my side torso area," he says.

Luckily, the shark "let go and swam away immediately," and Robles – who received numerous stitches on his chest and thumb where the shark tore through an artery – is alive to tell the story.

"I immediately started screaming, and about three swimmers who were five strokes behind me came up and helped me get to shore," he says. "A paddler showed up and got me on his longboard and paramedics and lifeguards were waiting."

Robles – who's been swimming that shoreline "his entire life" – is now back home recovering and feeling very lucky.

"Fortunately, the bite didn't go into any organs and I didn't crack any ribs," he says. "I'm very thankful I'm alive. This absolutely could have been it. I was given a second chance, and this is Day One of a new life."